The present invention relates to thermoplastic aromatic polysulfone resins. More precisely, it relates to thermoplastic aromatic polysulfone resins which have a reduced viscosity within a specific range and have a specific sum total of the number of phenolic hydroxyl groups and the number of metallic salts thereof per a repeating unit of the polymer.
Aromatic polysulfone resins have been used as constitutive materials for various coating substances, adhesives and composite materials, since they are not only excellent in heat resistance, flame retardation, chemical resistance and so on but also good in adhesion to materials such as metals, glass, ceramics, various resins and carbon compounds. In a utilization of the resin, for example, an organic solvent solution of the resin is applied onto a substrate, which is then subjected to heat treatment to cause molecular weight-increase i.e., further polymerization, followed by inactivation.
Among the aromatic polysulfone resin, particularly those having a phenolic hydroxyl group are applied to such use. As such thermoplastic aromatic polysulfone resins, those having a reduced viscosity (RV) and the sum total of the number of phenolic hydroxyl groups and the number of metallic salts thereof contained in 100 repeating units of the polymer of 0.41 and 0.9 (JP-A-47-1087), 0.49 and 1.02 (JP-A-50-40700), 0.16 and 12 (JP-A-52-16535), and 0.53 and 1 (JP-A-59-191767), respectively, etc, have been known.
These thermoplastic aromatic polysulfone resins, however, had problems that they require severe conditions for heat treatment, i.e. a high treatment and a long period of heating, and that matters insoluble in an organic solvent are formed which cause rough surface and insufficient adherence of coating when the organic solvent solution of the resin is applied onto a substrate.
The present inventors have conducted extensive studies for solving these problems. As the result, they have found the fact that, when a thermoplastic aromatic polysulfone resin having a specific reduced viscosity and a specific sum total of the number of phenolic hydroxyl groups and the number of metallic salts thereof per a repeating unit of the polymer is used, the molecular weight-increase and the inactivation can be attained under moderate conditions and that the formation of the insoluble matters which cause various defects can be avoided. The present invention has been completed based upon such facts.
The present invention provides a practically superior thermoplastic aromatic polysulfone resin which has a reduced viscosity (RV) of 0.36 to 0.45 dl/g and a sum total A of the number of phenolic hydroxyl groups and the number of metallic salts thereof contained in 100 repeating units of the polymer of 1.6 or more.
The thermoplastic aromatic polysulfone resin according to the present invention has a reduced viscosity (RV) of 0.36 to 0.45 dl/g.
The reduced viscosity (RV) herein refers to a value obtained by measuring a solution of a resin having a concentration of 1.0 g/100 ml in N,N-dimethylformamide with Ostwald""s viscosity meter at 25xc2x0 C.
When the aromatic polysulfone resin has a reduced viscosity (RV) higher than 0.45 dl/g, a gel-like material insoluble in solvents and infusible even at a high temperature is formed. This can be a cause of defects in use as a coating material, an adhesive and a composite material. When it has a reduced viscosity less than 0.36 dl/g, the effect of molecular weight-increase by heat treatment decreases and the treatment requires a higher temperature and a longer time. A reduced viscosity of 0.38 to 0.45 dl/g is preferred because the effect of molecular weight-increase by heat treatment is enhanced.
The thermoplastic aromatic polysulfone resin of the present invention has a sum total A of the number of phenolic hydroxyl groups and the number of metallic salts thereof contained in 100 repeating units of the polymer of 1.6 or more.
When the sum total is less than 1.6, the effect of molecular weight-increase by heat treatment decreases and the treatment requires a higher temperature and a longer time. Considering the molecular weight-increase effect, it is desirable that the sum total A and the reduced viscosity (RV) satisfy the following formula:
0.45/(RV)1.56xe2x89xa6Axe2x89xa60.74/(RV)1.56 
One repeating unit of the polymer in the aromatic polysulfone resin of the present invention has one xe2x80x94SO2xe2x80x94 group.
Examples of the repeating unit include those represented by the following formula (1) or (2):
(xe2x80x94Phxe2x80x94SO2xe2x80x94Phxe2x80x94Oxe2x80x94) xe2x80x83xe2x80x83(1) 
(xe2x80x94Phxe2x80x94SO2xe2x80x94Phxe2x80x94Oxe2x80x94Axe2x80x94Oxe2x80x94) xe2x80x83xe2x80x83(2) 
wherein Ph represents a para-phenylene group and A represents a group of the formula (3):
xe2x80x94Phxe2x80x2xe2x80x94(xe2x80x94Bxe2x80x94Phxe2x80x2xe2x80x94)mxe2x80x94xe2x80x83xe2x80x83(3) 
wherein Phxe2x80x2 represents a phenylene group, B represents a direct bond, an alkylene group having 1 to 3 carbon atoms, an oxygen atom or a sulfur atom, and m represents an integer of 1 to 3.
The aromatic polysulfone resin of the present invention can be produced according to a known manner. For example, it can be produced by a condensation polymerization of a divalent phenol compound having a sulfone group and another divalent compound by using a catalyst, such as an alkali metal carbonate and an alkali metal hydrogen carbonate, in a high polar organic solvent. Examples of the divalent phenol compound having a sulfone group include dihydroxydiphenylsulfone. Examples of the other divalent compound include dihalogenobenzenoid.
When the dihalogenobenzenoid compound is used as the other divalent compound, the amount of the dihalogenobenzenoid compound is preferably within a range of 80 to 110% by mol based on the divalent phenol compound.
Examples of the highly polar organic solvent includes dimethylsulfoxide, 1-methyl-2-pyrrolidone, sulfolane(1,1-dioxothiolane), 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, diethylsulfone, diisopropylsulfone and diphenylsulfone.
The alkali metal carbonate and hydrogen carbonate is preferably sodium carbonate, potassium carbonate, and the corresponding hydrogen carbonates.
Generally, the alkali metal carbonate or hydrogen carbonate is used in an amount providing at least 0.95 equivalent of alkali metal atom per a phenol group and preferably an amount providing an excess of 0.001 to 0.25 equivalent of alkali metal atom per a phenol group.
The specific reduced viscosity (RV) of the aromatic polysulfone resin of the present invention, i.e. 0.36 to 0.45 dl/g, can be attained, for example, by adjusting the conditions of the condensation polymerization, such as polymerization temperature, polymerization time, the amount or kind of the catalyst to be used and the molar ratio of the divalent phenol compound having a sulfone group and the other divalent compound. Although the concrete conditions of the condensation polymerization to attain the specific reduced viscosity (RV) vary depending on the kind of monomers etc., the conditions can be easily determined, for example, by conducting a preliminary experiment.
The specific sum total A of the aromatic polysulfone resin of the present invention, i.e. 1.6 or more, can be attained, for example, by adjusting the conditions of the condensation polymerization, such as those mentioned above. Although the conditions of the condensation polymerization to attain the specific reduced viscosity (RV) vary depending on the kind of monomers etc., the conditions can be easily determined, for example, by conducting a preliminary experiment.
The specific reduced viscosity (RV) and the specific sum total A of the aromatic polysulfone resin of the present invention can also be attained by mixing two or more kinds of aromatic polysulfone resins which have reduced viscosities (RV) and sum totals A different from each other. In this case, the reduced viscosity of the aromatic polysulfone resins to be mixed should be 0.45 dl/g or less. Methods for mixing in this case are not particularly limited and include, for example, mixing of powders to another powders, mixing utilizing a solution and the like.
The thermoplastic aromatic polysulfone resin of the present invention is preferably used as a particle having the average particle diameter of about 50 to 2,000 xcexcm. When the diameter is less than 50 xcexcm, insoluble matter tend to be formed due to the aggregation of the particles and the geling of the aggregated mass on preparing a solution, particularly a solution having a concentration of 20% by weight or more. When the diameter is more than 2,000 xcexcm, the dissolution of the resin takes longer time. More preferred diameter range is 100 to 1,000 xcexcm.
The thermoplastic aromatic polysulfone resin of the present invention is usually used as a solution of an organic solvent. Although the organic solvent used for preparing the solution is not particularly limited insofar as the solvent dissolves the resin, normally methylene chloride, 1,1,2-trichloroethane, N,N-dimethylformamide, 1-methyl-2-pyrrolidone, dimethylsulfoxide, pyridine, quinoline, aniline, o-chlorophenol, dimethylacetamide, diethylacetamide, anisol, xcex3-butyrolactone, dioxolane and the like are used as the organic solvent.
In the thermoplastic aromatic polysulfone resin of the present invention, the number of metallic salts of phenolic hydroxyl groups is preferably 25% or less of the sum total A of the number of phenolic hydroxyl groups and the number of metallic salts thereof contained in 100 repeating units of the polymer, for providing a solution of the resin of the present invention in an organic solvent having a lower viscosity.
The solvent can be used singly or in combination of two or more kinds of solvents. In order to prepare a coating having an excellent surface smoothness or a processing intermediate having excellent solution stability, it is preferred to use a mixture of two or more kinds of solvents. In this case, a solvent other than those exemplified above can be used insofar as the solubility of the thermoplastic aromatic polysulfone resin is adversely affected.
Methods for preparing the solution is an organic solvent is not particularly limited. For example, a solvent may be added to the resin or a resin may be added to a solvent.
When using the thermoplastic aromatic polysulfone resin of the present invention for preparing a coating, an adhesive, a composite material and the like, an additive can be added in order to provide them with various functions. Examples of such additive include dye, pigment, plasticizer, adsorbent for various rays, stabilizer and conductive material.
When the thermoplastic aromatic polysulfone resin of the present invention is used for a coating, an adhesive, a composite material or the like, a heat treatment is usually conducted after coating a substrate, binding the substrate with another substrate, mixing with another substance or the like to effect the molecular weight-increase an inactivation. Method for the heat treatment is not particularly limited. It is decided in view of various properties such as mechanical property, optical property and the like of coating, adhesion and composite material to be produced, performance or economy of apparatus for use in processing and the like.
Although temperature of the heating is not particularly limited and decided according to the use and performance of the apparatus, generally, the temperature is between 250xc2x0 C. and 450xc2x0 C. In particular, a temperature between 300xc2x0 C. and 400xc2x0 C. is preferred because a product with suitable molecular weight is produced and a degradation reaction such as coloring is suppressed. A temperature lower than 250xc2x0 C. is not preferred from the viewpoint of productivity because a longer time is requires for molecular weight-increase. A temperature higher than 450xc2x0 C. is not preferred because the degradation reaction of the resin tends to occur and problems such as coloring tend to be caused.
Atmosphere of the heating is not particularly limited. The heating may be conducted in air or in the absence of oxygen. The treatment under presence of oxygen sometimes allows shortening of the treating period.
The thermoplastic aromatic polysulfone resin of the present invention allows the molecular weight-increase and the inactivation by a heat treatment under moderate conditions. When it is dissolved in a solvent, the formation of the insoluble matters which causes various defects can be avoided. Therefore, the resin of the present invention is advantageous as a material for use in coating, adhesion, composite material or the like.